Optical fibers are currently used to transmit optical signals for a variety of applications. Optical fibers, including multimode optical fibers, are frequently used for data transmission (including high-speed data transmission) over distances ranging from one meter or less up to the distance needed to transmit throughout a building, e.g., a data center. The optical-fiber links (“links”) in present-day data centers are mostly “legacy links” designed to operate in the 850 nm wavelength window and utilize relatively inexpensive 850 nm VCSEL laser sources.
Unfortunately, optical fiber has relatively high chromatic dispersion in the 850 nm window, which leads to rapid broadening of the optical signals. This high chromatic dispersion is a key limitation on the maximum length of legacy links for high data modulation (data) rates, e.g., 25 Gb/s and higher. In addition, the fiber attenuation is relatively high at 850 nm, and this negatively impacts the performance when the legacy link is more than a few tens of meters.
To operate optical-fiber links at higher data modulation rates, it would be advantageous to convert the 850 nm legacy links to links that have high bandwidth at longer wavelengths, such as 1060 nm or 1310 nm. The 1310 nm window in particular offers a significant performance advantage over the 850 nm window due to its possessing near zero chromatic dispersion as well as relatively low attenuation. This is particularly important at data modulation rates of 25 Gb/s and higher, where dispersive broadening of the optical signals results in large impairments. In addition, high data-rate systems employing silicon-photonic transceivers in the 1310 nm window advantageously require much less electrical power than do conventional transceivers operating at 850 nm.
While in principle it is possible for data-center operators to swap out all the optical-fiber cables optimized for 850 nm VCSELs with new optical-fiber cables optimized for 1310 nm, this approach is costly and labor intensive. Much of the optical-fiber cabling runs beneath floors and other hidden portions of the building in which the data center resides. Further, the existing optical-fiber cabling in just one data center represents thousands of kilometers of optical fiber cabling that would need to be replaced.